Lamp filament connection



June 15, 1965 w. L.. Bai-@memes LAMP FILAMEFQT CONNECTION F1165, mh 9,9;3.962

A Wim FIG. 2.

INVENTOR. W/ l /HM @RUND/6E.

United States Patent O gna This invention relates to electrical devicesand, more particularly, to an improved mechanical and electricalconnection between the filament and lead-in conductor or supportingmember of an incandescent electric lamp.

ln the manufacture of certain types of electric lamps, such ashigh-Wattage tubular heat lamps having coiled laments of relativelyheavy wire for example, 'the size and rigidity of the lead-in conductormakes it dicult to connect it to the filament. Que frequently usedmethod ot joining these members together is to enlarge the end of theconductor and force it into the coil until it becomes caught behind theend turns of the lament. A juncture of this type wherein the end of theconductor is flattened to provide a spade-like tip that efiects aforce-ht with the ilament coil is disclosed in US. Patent No. 2,830,217,issued April 8, 1958.

Another and older method of etiecting such junctures is to form threadson the end of the conductor either by a cutting operation or by windinga wire tightly around the conductor at the proper pitch. The threadedend of the conductor is then screwed into the end of the coiled lilamentthus threadably coupling the members together. Threaded conductors andconnections or" this character are illustrated and described in US.Patent llo. 2,449,679, issued September 2l, 1948.

The lead-tolament connection has also been etlected in some cases byWelding the members together.

lt is accordingly the general object of this invention to provide animproved iilarnent connection that does not require a criticaldimensional t of the members and thus eliminates this problem andovercomes other disadvan tages of the prior art structures.

A more specitic object is the provision of a ilament juncture that issimple, inexpensive, and reliably locks the members in oppositeelectrical engagement without any additional parts or criticalinteriitting of the members.

The foregoing objects, and others which will become obvious as thedescription proceeds, are achieved in accordance with this invention byproviding a recess and a pair of abrupt transverselyextending shouldersat a preselected point along the conductor, inserting this recessedportion into the coiled lilament, and then permanently deforrning andcollapsing intermediate portion of the lilament into the recess. rlhepartly flattened lilament portion is retained Within the recess by theshoulders thereby securely locking the members together in electricalengagement and preventing the filament from slipping along the conductorin either direction.

The recess and retaining shoulders can be formed at the same time thatthe lilarnent turns are collapsed by simultaneously applying sutlicientheat and pressure to the filament turns and the underlying portion ofthe inserted conductor, preferably in the presence of an inertatmosphere.

A better understanding of the invention will be obtained by referring tothe accompanying drawing where 1n:

EEG. l is an elevational view of one form ol' electric lamp embodying myinvention, a central portion ot the lamp being omitted for convenienceof illustration;

FIG. 2 is an enlarged perspective View of the connecting end ci alead-in conductor in accordance with one embodiment ot the invention;

3 is a cross-sectional view of the conductor taken alo.-g the linelll-lll of FIG. 2, in the direction of tn arrows;

EG. 4 is a plan View of the conductor shown in FIGS. 2 and 3 connectedwith one end of the coiled filament in accordance with this invention;

FiG. 5 is a view corresponding to that shown in FIG. 4 but with aportion of the filament omitted for illustrative purposes;

FIG. 6 is a cross-sectional view of the connection along the line fl-Vlof FlG. 4;

FlG. 7 is an elevational view ot another type of juncture according tothe invention; and

FiG. S is an enlarged cross-sectional view along the line Vill-Vlll ofFIG. 7, in the direction of the arrows.

While the improved lament connection of this invention can be employedin various types ot lamps and electrical devices, it is especiallysuited for use in conjunction with high-vvattage tubularinfrared-generating lamps and has accordingly been so illustrated andwill be so described.

With specific reference to the drawing, in FlG. l there is illustrated atubular heat lamp 1@ comprising a quartz e '-felope l1. of relativelysmall diameter that is closed at each end by a press seal i4. SealedWithin the envelope is a coiled filament 13 of helical configurationWound from a suitable refractory metal wire, such as tungsten forexample. The filament extends longitudinally of the envelope and iscentrally mounted therein by means or" lead-in conductors 16 ofmolybdenum or the lilre embedded in each of the press seals and by aplurality of spaced supporting discs 2li ot tantalum, or other suitablerefractory material, that are inserted between adjacent turns of and areanchored to the lilament at preselected points along its length. Thelead-in conductors 16 are fastened to the usual ribbon-and-terminalassemblies embedded in each of the press seals to facilitate connectingthe lamp to a voltage source. In order to prevent the ilament 15 fromsagging during use, the lead-in conductors lo are so spaced during thesealing-in operation that the lament is tensioned slightly and kepttaut. The envelope contains the usual filling of a suitable inert gassuch as argon or the like.

A detailed description of a lamp of the foregoing type is given in US.Patent No. 2,864,025 dated December 9, S.

ln accordance with one form of the present invention a preselectedportion of each of the lead-in conductors il@ 1s deformed to provide allat 22 proximate to, but spaced mwa' ly from one end of the conductor,as shown in 3. The reduction in cross-section of this that in the caseot a conductor wire i6 or the lille having a substantially uniformdiameter d1, a fiat opredetermined length L, width W, and thickness t isprovided, as is illustrated. Preferably, the reduction in cross sectionof the wire is such that the thickness t of the iiat 22 is no greaterthan about Vs of the wire diameter d1 so as to form pronounced recesses23 (see llG. 3) on opposite sides of the conductor, which recesses areterminated at each end by transversely c2 extending shoulder that areWell delinea rise abruptly from the ilat The rounded coiour of theconductor is, accordingly, abroA tly altere.. by the s" .t

whereas the extreme end portion 2d of the conductor slightly smallerthan the inner diameter 2 of coiled ilament lo so that the llattenedportion of the conductor le can very readily be inserted into th endsection of li that it extends for a plurality of turns of the fil suchas three turns thereof as in the case illu FGS. 4 to 6.

To er'iect the juncture according to the embodiment shown in FiGS. 4 tod, the ilattened portion of the conductor is iirst inserted into thecoiled filament and positioned so that the flat Z2. is located beyondthe end turns and within an intermediate portion 28 of the filament. Thelament turns comprising the overlying intermediate portion are thenpermanently deformed and partly collapsed by simultaneously heating thisportion of the filament and compressing it in a direction substantiallynormal to the surface of the iat. ln order to avoid deleteriouslyoxidizing the filament or conductor, heating and bending of the filamentturns is preferably performed in an inert atmosphere such as nitrogen.

The aforesaid heating and compressing operation partly collapses theintermediate portion 2S of the filament it@ into :the recesses 23 andforces the bent turns into intimate engagement with the dat Z2, asillustrated in FGS. 4 to 6. Moreoven'as shown most particularly in FlG.6, the outermost turns of the collapsed intermediate portion 28 of thetilament are caught and seated behind the transversely extendingshoulders 26 located at each end of the flat thus securely locking thecollapsed turns within the recesses and coupling the filament andconductor wire in positive electrical and mechanical engagement.

Heating and bending of the filament turns that com-y prise theintermediate portion 2d can be conveniently accomplished by means of lapair of `suitably shaped jaws (not shown) having electrically heatedwork faces.

As a `specific example of the actua-l dimensions involved, in the caseof a 5 G0 watt infrared heat lamp having a lead-in Wire 0.025 indiameter a coil with an inside diameter of about 0.040 Wound fromtungsten Wire .0098 in diameter, satisfactory connections have heenobtained by employing a dat approximately 1/16 long, 0.035" Wide andabout 0.015 thick.

ht should be noted that the intermediate portion of the filament to becollapsed need only be heated sufficiently to render it easilydeformable. rihus, temperatures in the order of approximately 200 C. inthe case of a tungsten filament Will sufllce.

As shown in the alternative embodiment illustrated in FIGS. 7 and 8, thedesired mechanical and electrical juncture can also be achieved inaccordance with this invention by utilizing a straight or unmodied pieceof conductor wire 16a, that is, one which is not provided with a ilat ordeformed portion near one end. The conductor wire in this case isfabricated from a relatively soit metal such as annealed nickel, copperor the like and has a diameter d3 that is slightly less than the insidediameter d2 of the iilament ld, as indicated in E2G. 7.

After the end of the conductor lo has been inserted into the properposition within an intermediate portion 23a of the filament this portionand the underlying segment of the conductor are simultaneously heatedand coinpressed along a line normal to the wire axis until the partlycollapsed lameut turns are at least partly embedded in the conductor ata plurality of points 3l) located on opposite sides of the conductor andinward from its proximate end7 as shown in FIG. 7. The applied heat andpressure are such that the distance :c between in the same direction asth considerably less cl3 of 'the Wire, as indicated in Flo `ity oftransverse grooves are ii conductor by the col- A ent tu Thus, in thisembodiment the deformation of the conductor and partial collapse of theoverlying intermediate portion of the filament are both accomplished bymeans of a sirele operation. will be obvious from FlG. 7 that i, heatand pressure are applied lto form the same combination of pronouncedrecesses and abrupt retaining shoulders las in the case of the firstembodi ient shown in fFlG-S. l to 6.

` nient Att* i g-oaci. and resul-tnt during the cooling-down it will oeobvious, of course, that the aforementioned ed in the surface of theconductor,

by stamping, to provide a preformed conductor as in `ofthe b ment shownin FEES, Z to 6.

om the foregoing that vthe objects of toe inven have been achieved byproviding an improved electrical and mechanical junction between a mentand lead-in conductor or support which conand inexper 7e to fabricate.

embodiments of the improved conbeen described in detail, these are givenhave nection merely by Way of example and various structural andprocedural modifications can accordingly be made without departing tromthe spirit and scope of this invention. For example, Ithe iilarnent doesnot have to be coiled throughout its length but may be provided withcoiled end sections that `are interlocked with the lead-in member in themanner described.

l claim as my invention: Y

Il. In an electric incandescent lamp, the combination of a refractorywire filament having a coiled end section, and a lead-in conductor thatis smaller in diameter than the inside diameter of said coiled endsection and has a flat that is located proximate but inv/ard from oneend of said conductor aud lits freely within said coiled end section,the rounded contour of said lead-in conductor being abruptly altered bysaid tlat thereby .providing an elongated recess that is terminated ateach end by transversely-extending sharply-defined shoulder, said beinglocated within an intermediate portion of said coiled end section and ofsuflicient length to accommodate more than one turn of said coiled endsection, the turns of said coiled end secon overlying said fiat beingcollapsed into recess seated between said shoulders thereby loclcinfr`said conductor in mechanical and positive electrical engagement withsaid iilament.

2. ln combination with a iilament of refractory metal Wire having acoiled end section comprising a plurality of spaced turns, a conductorthat is freely insertable into said coil end section and has an`elongated recess Which is located proximate to but inward from one endof said conductor and is defined by a pair of abrupttransverselyextending shoulders, said conductor being inserted into saidcoiled end section a distance such that the recessed portion of saidconductor is loc-ted Within an intermediate portion of said coiled endsection and the proximate end portion of said conductor projectstherebeyond toward the filament proper, a plurality of the tumscomprising the overlying intermediate portion of said coiled end sectionbeing permanently deformed and collapsed into said recess and seatedtherein between and in interlocking relationship with said shoulders,thereby mechanical- 6 References Cited by the Examiner UNITED STATESPATENTS 1,379,036 5/21 Moorhead 313-333 X 2,667,592 1/54 Hilder 313-344X 5 2,830,217 4/58 Hodge 313-333 X 2,864,025 12/58 Foote et al 313-274DAVID I. GALVIN, Primary Examiner. JOHN W. HUCKERT, ARTHUR GAUSS,Examiners.

1. IN AN ELECTRIC INCANDESCENT LAMP, THE COMBINATION OF A REFRACTORYWIRE FILAMENT HAVING A COILED END SECTION, AND A LEAD-IN CONDUCTOR THATIS SMALLER IN DIAMETER THAN THE INSIDE DIAMETER OF SAID COILED ENDSECTION AND HAS OF FLAT THAT IS LOCATED PROXIMATE BUT INWARD FROM ONE OFSAID CONDUCTOR AND FITS FREELY WITHIN SAID COILED END SECTION, THEROUNDED CONTOUR OF SAID LEAD-IN CONDUCTOR BEING ABRUPTLY ALTERED BY SAIDFLAT THEREBY PROVIDING AN ELONGATED RECESS THAT IS TERMINATED AT EACHEND BY A TRANSVERSELY-EXTENDING SHARPLY-DEFINED SHOULDER, SAID FLATBEING LOCATED WITHIN AN INTERMEDIATE PORTION OF SAID COILED END SECTIONAND OF SUFFICIENT LENGTH TO ACCOMMODATE MORE THAN ONE TURN OF SAIDCOILED END SECTION, THE TURNS OF SAID COILED END SECTION OVERLYING SAIDFLAT BEING COLLAPSED INTO RECESS AND SEATED BETWEEN SAID SHOULDERSTHEREBY LOCKING SAID CONDUCTOR IN MECHANICAL AND POSITIVE ELECTRICALENGAGEMENT WITH SAID FILAMENT.